U.S. patent application number 10/648421 was filed with the patent office on 2005-03-03 for method of patterning an electroconductive layer on a support.
This patent application is currently assigned to Eastman Kodak Company. Invention is credited to Anderson, Charles C., Burberry, Mitchell S., Lelental, Mark.
Application Number | 20050048406 10/648421 |
Document ID | / |
Family ID | 34216728 |
Filed Date | 2005-03-03 |
United States Patent
Application |
20050048406 |
Kind Code |
A1 |
Burberry, Mitchell S. ; et
al. |
March 3, 2005 |
METHOD OF PATTERNING AN ELECTROCONDUCTIVE LAYER ON A SUPPORT
Abstract
An element for making patterns on an electroconductive
substrate, the element comprising a support, on which is disposed:
a) a conductive layer containing an electrically conductive
polymer, a polyanion and a conductivity enhancing agent; and b) a
mixing layer containing a thermally mobile material; wherein, upon
imagewise heating the mixing layer, the thermally mobile material
mixes with the conductive layer, thereby causing the initial
surface resistivity (SR) of the conductive layer to imagewise
increase from an initial value SR.sub.i, which is lower than
10.sup.5 .OMEGA./square, to SR.sub.i.DELTA., .DELTA. being at least
10.sup.2.
Inventors: |
Burberry, Mitchell S.;
(Webster, NY) ; Anderson, Charles C.; (Penfield,
NY) ; Lelental, Mark; (Rochester, NY) |
Correspondence
Address: |
Paul A. Leipold
Patent Legal Staff
Eastman Kodak Company
343 State Street
Rochester
NY
14650-2201
US
|
Assignee: |
Eastman Kodak Company
|
Family ID: |
34216728 |
Appl. No.: |
10/648421 |
Filed: |
August 26, 2003 |
Current U.S.
Class: |
430/311 |
Current CPC
Class: |
H05K 3/105 20130101;
H01L 51/0037 20130101; H05K 3/02 20130101; H01L 51/0015 20130101;
H05K 2201/0329 20130101; Y10S 430/165 20130101 |
Class at
Publication: |
430/311 |
International
Class: |
G03C 005/00 |
Claims
What is claimed is:
1. An element for making patterns on an electroconductive
substrate, the element comprising a support, on which is disposed:
a) a conductive layer containing an electrically conductive
polymer, a polyanion and a conductivity enhancing agent; and b) a
mixing layer containing a thermally mobile material; wherein, upon
imagewise heating the mixing layer, the thermally mobile material
mixes with the conductive layer, thereby causing the initial
surface resistivity (SR) of the conductive layer to imagewise
increase from an initial value SR.sub.i, which is lower than
10.sup.5 Q/square, to SR.sub.i.DELTA., .DELTA. being at least
10.sup.2.
2. The element of claim 1 patterned for use in an electronic or
semiconductor device.
3. The element of claim 1 patterned for use as a printed circuit
board, an integrated circuit, a display, an electroluminescent
device or a photovoltaic cell.
4. The element of claim 1 wherein the thermally mobile material is
contained in a polymeric matrix.
5. The element of claim 4 wherein the polymeric matrix comprises a
crosslinked or branched polymer.
6. The element of claim 5 wherein the crosslinked polymer is
poly(styrene-co-indene-co-divinylbenzene),
poly(styrene-co-acrylonitrile-- co-divinylbenzene),
poly(styrene-co-butadiene-co-divinylbenzene).
7. The element of claim 1 wherein the thermally mobile material is
a pigment, a dye, or a combination of both.
8. The element of claim 4 wherein the polymeric matrix is a
thermally mobile material.
9. The element of claim 1 wherein the thermally mobile material has
recurring units of the following formula: 5wherein: R.sup.1
represents cyano, isocyanate, azide, sulfonyl, nitro, phosphoric,
phosphonyl, heteroaryl, or 6where X is O, S, NR, or N.sup.+
(R).sub.2; R.sup.3 is R, OR, O--M.sup.+, OCOOR, SR, NHCOR,
NHCON(R).sub.2, N(R).sub.2 or N.sup.+ (R).sub.3; M.sup.+ is an
alkali or ammonium moiety; R is hydrogen, halogen, or an alkyl or
cycloalkyl group; and R.sup.2 is hydrogen, alkyl or from the same
list as R.sup.1.
10. The element of claim 1 wherein the conductive layer contains an
optional film-forming polymeric binder.
11. The element of claim 1 wherein the conductivity enhancing agent
is an organic compound containing dihydroxy, poly-hydroxy,
carboxyl, amide, or lactam groups.
12. The element of claim 1 wherein the organic compound containing
dihydroxy, poly-hydroxy, carboxyl, amide, or lactam groups is: (a)
represented by the following Formula II: (OH).sub.n--R--(COX).sub.m
II wherein m and n are independently an integer of from 1 to 20, R
is an alkylene group having 2 to 20 carbon atoms, an arylene group
having 6 to 14 carbon atoms in the arylene chain, a pyran group, or
a furan group, and X is --OH or --NYZ, wherein Y and Z are
independently hydrogen or an alkyl group; or (b) a sugar, sugar
derivative, polyalkylene glycol, or glycerol compound; or (c)
selected from the group consisting of N-methylpyrrolidone,
pyrrolidone, caprolactam, N-methyl caprolactam, or
N-octylpyrrolidone.
13. The element of claim 1 wherein said conductivity enhancing
agent is a N-methylpyrrolidone, pyrrolidone, caprolactam,
N-methylcaprolactam, N-octylpyrrolidone, sucrose, glucose,
fructose, lactose, sugar alcohol, 2-furan carboxylic acid, 3-furan
carboxylic acid, sorbitol, glycol, ethylene glycol, glycerol,
diethylene glycol, or triethylene glycol, or a mixture of any two
or more of these compounds.
14. The element of claim 1 wherein said conductivity enhancing
agent is N-methylpyrrolidone, pyrrolidone, caprolactam, N-methyl
caprolactam, or N-octylpyrrolidone.
15. The element of claim 1 wherein said conductivity enhancing
agent is ethylene glycol, diethylene glycol or glycerol.
16. The element of claim 1 wherein said conductivity enhancing
agent is one or more than one compound selected from the group
consisting of N-methylpyrrolidone, sorbitol, ethylene glycol,
glycerol, and diethylene glycol.
17. The element of claim 5, wherein n and m independently of one
another denote an integer from 2 to 8.
18. The element of claim 11 wherein the organic compound containing
lactam groups is n-methylpyrrolidone, pyrrolidone, caprolactam,
n-methylcaprolactam, or n-octylpyrrolidone.
19. the element of claim 12 wherein the conductivity enhancing
agent is sucrose, glucose, fructose, lactose, sorbitol, mannitol,
2-furancarboxylic acid, 3-furancarboxylic acid, ethylene glycol,
glycerol, di- or triethylene glycol. solution.
20. The element of claim 1 wherein the conductive polymer is a
substituted or unsubstituted pyrrole-containing polymer, a
substituted or unsubstituted thiophene-containing polymer, or a
substituted or unsubstituted aniline-containing polymer.
21. The element of claim 1 wherein the layer containing the
conductive polymer contains 10 to 1000 mg/m2 dry coating weight of
the conductive polymer.
22. The element of claim 1 wherein the layer containing the
conductive polymer contains 20 to 500 mg/m.sup.2 dry coating weight
of the conductive polymer.
23. The element of claim 1 wherein the layer containing the
conductive polymer comprises a mixture containing: a) a
polythiophene according to Formula I; 7wherein each of R.sup.1 and
R.sup.2 independently represents hydrogen or a C1-C4 alkyl group or
together represent an optionally substituted C1-C4 alkylene group
or a cycloalkylene group, preferably an ethylene group, an
optionally alkyl-substituted methylene group, an optionally C1-C12
alkyl- or phenyl-substituted 1,2-ethylene group, a 1,3-propylene
group or a 1,2-cyclohexylene group, and n is 5-1000; b) a polyanion
compound; and, optionally c) a film forming polymeric binder.
24. The element of claim 23 wherein the polyanion is an anion of a
polymeric carboxylic acid.
25. The element of claim 23 wherein the polyanion is a polyacrylic
acid, a poly(methacrylic acid), a poly(maleic acid), or a polymeric
sulfonic acid.
26. The element of claim 23 wherein the polyanion is a
polystyrenesulfonic acid or a polyvinylsulfonic acid.
27. The element of claim 23 wherein the film-forming polymeric
binder comprises from 5 to 95 wt % of the layer containing the
conductive polymer.
28. The element of claim 23 wherein the film-forming polymeric
binder is selected from the group consisting of water-soluble or
water-dispersible hydrophilic polymers, maleic acid or maleic
anhydride copolymers, cellulose derivatives, polyvinyl alcohol, and
poly-N-vinylpyrrolidone.
29. The element of claim 23 wherein the film-forming polymeric
binder is gelatin or gelatin derivatives.
30. The element of claim 23 wherein the film-forming polymeric
binder is carboxymethyl cellulose, hydroxyethyl cellulose,
cellulose acetate butyrate, diacetyl cellulose, or triacetyl
cellulose.
31. The element of claim 23 wherein the film-forming polymeric
binder is an aqueous emulsion of addition-type homopolymers and
copolymers prepared from ethylenically unsaturated monomers.
32. The element of claim 31 wherein the monomers are selected from
the group consisting of acrylates, methacrylates, acrylamides,
methacrylamides, itaconic acid and its half-esters and diesters,
substituted and unsubstituted styrenes, acrylonitrile,
methacrylonitrile, vinyl acetates, vinyl ethers, vinyl and
vinylidene halides, and olefins.
33. The element of claim 23 wherein the film-forming polymeric
binder is an aqueous dispersion of polyurethanes or
polyesterionomers.
34. The element of claim 1 wherein the support is transparent,
opaque, or reflective.
35. The element of claim 1 wherein the support is glass, a
polymeric film, paper, silicon wafers, or glass reinforced
epoxy.
36. The element of claim 35 wherein the polymeric film support is
polyester, polycarbonate, polystyrene, cellulose esters, or
polyolefins.
37. The element of claim 1 wherein the support is flexible or
rigid.
38. The element of claim 1 wherein the support comprises cellulose
acetate, poly(ethylene terephthalate) or poly(ethylene
naphthalate).
39. The element of claim 1 wherein the support is
surface-treated.
40. The element of claim 1 wherein the support is between 50 .mu.m
and 254 .mu.m thick.
41. The element of claim 1 wherein the dry coverage of the
conductive layer is between 0.002 and 0.5 g/m2.
42. The element of claim 1 wherein the conductive layer is coated
from a dispersion of a conductive polymer in water, alcohol or
acetone.
43. A method of patterning an electroconductive layer on a support,
the support having thereon a mixing layer containing a thermally
mobile material and a conductive polymer layer containing a
polythiophene), a polyanion and a di- or polyhydroxy organic
compound, whereby the mixing layer is heated image-wise in selected
areas, causing the thermally mobile material to mix with the
conductive layer, wherein; the surface resistivity (SR) of the
conductive layer is decreased or increased from an initial value
SR.sub.i, which is lower than 10.sup.4 .OMEGA./square to
SR.sub.i.DELTA., .DELTA. being at least 10.sup.3 in said selected
areas without substantially ablating or destroying the polymer
layers.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application relates to commonly assigned copending
application Ser. No. ______ (DN 83892) entitled PHOTOPATTERNING OF
CONDUCTIVE ELECTRODE LAYERS CONTAINING ELECTRICALLY-CONDUCTIVE
POLYMER PARTICLES, application Ser. No. ______ (DN 83943) entitled
ELECTROGRAPHIC PATTERNING OF CONDUCTIVE ELECTRODE LAYERS CONTAINING
ELECTRICALL-CONDUCTIVE POLYMERIC MATERIALS, application Ser. No.
______ (DN83879) entitled PATTERNING OF ELECTRICALLY CONDUCTIVE
LAYERS BY INK PRINTING METHODS, filed simultaneously herewith. The
copending applications are incorporated by reference herein for all
that they contain.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for patterning an
organic polymer electroconductive layer that is suitable as an
electronic circuitry element in an electric or semiconductor
device.
BACKGROUND OF THE INVENTION
[0003] Electric or semiconductor devices such as flat panel
displays, photovoltaic cells or electrochromic windows typically
contain a substrate provided with an indium tin oxide (ITO) layer
as a transparent electrode. The coating of ITO is carried out by
vacuum sputtering methods which involve high temperature conditions
up to 250.degree. C., and therefore, glass substrates are generally
used. The high cost of the fabrication methods and the low
flexibility (pliability) and stretchability of such electrodes, due
to the brittleness of the inorganic ITO layer as well as the glass
substrate, limit the range of potential applications. As a result,
there is a growing interest in making all-organic devices,
comprising plastic resins as a substrate and organic
electroconductive polymer layers as an electrode. Such plastic
electronics allow low cost devices with new properties (Physics
World, March 1999, p.25-39). Flexible plastic substrates can be
provided with an electroconductive polymer layer by continuous
roller coating methods (compared to batch process such as
sputtering) and the resulting organic electrodes enable the
fabrication of electronic devices characterized by a higher
flexibility and a lower weight.
[0004] The production and the use of electroconductive polymers
such as polypyrrole, polyaniline, polyacetylene, polyparaphenylene,
polythiophene, polyphenylenevinylene, polythienylenevinylene and
polyphenylenesulfide are well known in the art. EP-A-440 957
describes a method for preparing polythiophene in an aqueous
mixture by oxidative polymerization in the presence of a polyanion
as a doping agent. In EP-A-686 662 it has been disclosed that
highly conductive layers of polythiophene, coated from an aqueous
coating solution, could be made by the addition of a di- or
polyhydroxy and/or a carbonic acid, amide or lactam group
containing compound in the coating solution of the polythiophene
layer and by keeping the coated layer at elevated temperature,
preferably between 100 and 250.degree. C., during preferably 1 to
90 seconds.
[0005] Coated layers of organic electroconductive polymers can be
structured into patterns using the known wet-etching
microlithography techniques. WO97/18944 describes a process wherein
a positive or negative photoresist is applied on top of a coated
layer of an organic electroconductive polymer, and after the steps
of selectively exposing the photoresist to UV light, developing the
photoresist, etching the electroconductive polymer layer and
finally stripping the non-developed photoresist, a patterned layer
is obtained. A similar technique has been described in Synthetic
Metals, 22 (1988), p. 265-271 for the design of an all-organic
thin-film transistor. Such methods are cumbersome as they involve
many steps and require the use of hazardous chemicals. Research
Disclosure No. 1473 (1998) describes photoablation as a method
suitable for patterning organic electroconductive polymer layers,
wherein the selected areas are removed from the substrate by laser
irradiation. Such photoablation processes are convenient, dry,
one-step methods but the generation of debris still requires a wet
cleaning step and may contaminate the optics and mechanics of the
laser structuring device. Some prior art methods also induce a
difference of the optical density between electroconductive and
non-conductive areas of the patterned surface, which should be
avoided. Methods of patterning organic electroconductive polymer
layers by image-wise heating by means of a laser have been
disclosed in EP 1 079 397 A1. That method induces a decrease in
resistivity without substantially ablating or destroying the layer.
It is limited however to modest changes of resistivity between
imaged and unimaged areas of about 3 orders of magnitude.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a
convenient, dry, one-step method of patterning an electroconductive
organic polymer layer which does not require a wet cleaning step,
has little influence on the optical density of the polymer layer,
has very high contrast between conductive and resistive regions and
does not require the removal of the conductive layer.
[0007] A method of patterning an electroconductive layer on a
support is disclosed. The support is provided with a mixing layer
containing a thermally mobile material, and a conductive polymer
layer containing a polythiophene, polyanion and a di- or
polyhydroxy organic compound. The conductive layer is characterized
by an initial surface resistivity (SR.sub.i) having a value that is
lower than 10.sup.4 .OMEGA./square. By heating selective areas of
the mixing layer the surface resistivity of these areas is
increased to SR.sub.i.DELTA. wherein .DELTA. is at least 10.sup.3,
preferably at least 10.sup.5 and more preferable at least 10.sup.8.
The electroconductive pattern thus obtained can be used as an
electronic circuit for making an electronic or semiconductor device
such as a printed circuit board, an integrated circuit, a display,
an electroluminescent device or a photovoltaic cell.
[0008] The invention provides:
[0009] An element for making patterns on an electroconductive
substrate, the element comprising a support, on which is
disposed:
[0010] a) a conductive layer containing an electrically conductive
polymer, a polyanion and a conductivity enhancing agent; and
[0011] b) a mixing layer containing a thermally mobile material;
wherein, upon imagewise heating the mixing layer, the thermally
mobile material mixes with the conductive layer, thereby causing
the initial surface resistivity (SR) of the conductive layer to
imagewise increase from an initial value SR.sub.i, which is lower
than 10.sup.5 .OMEGA./square, to SR.sub.i.DELTA., .DELTA. being at
least 10.sup.2.
[0012] Also provided is a method of patterning an electroconductive
layer on a support, the support having thereon a mixing layer
containing a thermally mobile material and a conductive polymer
layer containing a polythiophene), a polyanion and a di- or
polyhydroxy organic compound, whereby the mixing layer is heated
image-wise in selected areas, causing the thermally mobile material
to mix with the conductive layer, wherein;
[0013] the surface resistivity (SR) of the conductive layer is
decreased or increased from an initial value SR.sub.i, which is
lower than 10.sup.5 .OMEGA./square to SR.sub.i.DELTA., .DELTA.
being at least 10.sup.2 in said selected areas without
substantially ablating or destroying the polymer layers.
[0014] Further advantages and embodiments of the present invention
will become apparent from the following description and
examples.
DETAILED DESCRIPTION OF THE INVENTION
[0015] All values of surface resistivity (SR) presented in this
document are measured at 20.degree. C. and 50% relative humidity
according to the two-point probe method using knife edge electrodes
approximately 1 inch long with a 0.25 inch spacing between the
electrodes.
[0016] In this method of patterning an electroconductive polymer
layer, a support is provided with a mixing layer containing a
thermally mobile material and a conductive layer containing a
polythiophene, a polyanion and a di- or polyhydroxy organic
compound whereby; the mixing layer is selectively heated, causing
the thermally mobile material to mix with the conductive layer,
wherein the surface resistivity (SR) of the conductive layer is
increased at said selected areas from an initial value SR.sub.i,
which is lower than 10.sup.5 .OMEGA./square to SR.sub.i.DELTA.,
.DELTA. being at least 10.sup.2, preferably at least 10.sup.5 and
more preferable at least 10.sup.8 without substantially ablating,
removing or destroying the polymer layers. The mixing layer can be
provided with a polymeric matrix to contain the thermally mobile
material. In one embodiment the mixing layer is heated by means of
a resistive head array. In a more preferred embodiment the mixing
layer is also provided with a light-to-heat converting material
such as a dye, IR dye or pigment and the layer is heated by means
of a focused laser beam. In this embodiment the mixing layer is
heated by means of a focused laser beam.
[0017] The polymeric matrix in which the thermally mobile material
used in the invention is suspended can be any polymer material that
resists diffusion of the thermally mobile material at room
temperature. Matrix materials useful in the invention include
organic or inorganic polymers. Polymers which can be used in the
invention include the following: poly(vinyl chloride),
poly(vinylidene chloride), poly(vinyl chloride-co-vinylidene
chloride), chlorinated polypropylene, poly(vinyl chloride-co-vinyl
acetate), poly(vinyl chloride-co-vinyl acetate-co-maleic
anhydride), ethyl cellulose, cellulose acetate propionate,
nitrocellulose, poly(acrylic acid) esters, linseed oil-modified
alkyd resins, rosin-modified alkyd resins, phenol-modified alkyd
resins, phenolic resins, polyesters, polyisocyanate resins,
polyurethanes, poly(vinyl acetate), polyamides, chroman resins, gum
damar, ketone resins, maleic acid resins, polyvinylacetal,
polyvinylbutyral, vinyl polymers such as polystyrene and
polyvinyltoluene or copolymers of vinyl polymers with methacrylates
or acrylates, low-molecular weight polyethylene, phenol-modified
pentaerythritol esters, poly(styrene-co-indene-co-acrylonitrile),
poly(styrene-co-indene)- , poly(styrene-co-acrylonitrile),
copolymers with siloxanes, polyalkenes and
poly(styrene-co-butadiene), cross-linked gelatin, xanthum gum
(available commercially as Keltrol.RTM. from Kelco-Merck Co.),
poly(vinyl alcohol), polyester ionmers, polyglycols,
polyacrylamides, polyalkylidene-etherglycols, polyacrylates, etc.
The above matrix materials may be used either alone or in
combination. To increase the cohesion of the matrix layer, polymers
which are crosslinked or branched can be used such as
poly(styrene-co-indene-co-divinylbenzene),
poly(styrene-co-acrylonitrile-co-divinylbenzene),
poly(styrene-co-butadie- ne-co-divinylbenzene), etc.
[0018] Thermally mobile materials useful in the invention include
both pigments and dyes. Pigments which can be used in the invention
are desirably meltable or diffusible in the polymer matrix and
include the following: organic pigments such as metal
phthalocyanines, e.g., copper phthalocyanine, quinacridones,
epindolidiones, Rubine F6B (C.I. No. Pigment 184); Cromophthal.RTM.
Yellow 3G (C.I. No. Pigment Yellow 93); Hostaperm.RTM. Yellow 3G
(C.I. No. Pigment Yellow 154); Monastral.RTM. Violet R(C.I. No.
Pigment Violet 19); 2,9-dimethylquinacridone (C.I. No. Pigment Red
122); Indofast.RTM. Brilliant Scarlet R6300 (C.I. No. Pigment Red
123); Quindo Magenta RV 6803; Monstral.RTM. Blue G (C.I. No.
Pigment Blue 15); Monstral.RTM. Blue BT 383D (C.I. No. Pigment Blue
15); Monstral.RTM. Blue G BT 284D (C.I. No. Pigment Blue 15);
Monstral.RTM. Green GT 751 D (C.I. No. Pigment Green 7) or any of
the materials disclosed in U.S. Pat. No. 5,171,650, 5,672,458 or
5,516,622, the disclosures of which are hereby incorporated by
reference. Dyes useful in the invention include the following:
Anthraquinone dyes, e.g., Sumikaron Violet RS.RTM. (product of
Sumitomo Chemical Co., Ltd.), Dianix Fast Violet 3R-FS.RTM.
(product of Mitsubishi Chemical Industries, Ltd.), and Kayalon
Polyol Brilliant Blue N-BGM.RTM., and KST BlackI46.RTM. (products
of Nippon Kayaku Co., Ltd.); azo dyes such as Kayalon Polyol
Brilliant Blue BM.RTM., Kayalon Polyol Dark Blue 2BM and KST Black
KR.RTM. (products of Nippon Kayaku Co., Ltd.), Sumikaron Diazo
Black 5G.RTM. (product of Sumitomo Chemical Co., Ltd.), and
Miktazol Black5 GH.RTM. (product of Mitsui Toatsu Chemicals, Inc.);
direct dyes such as Direct Dark Green B.RTM. (product of Mitsubishi
Chemical Industries, Ltd.) and Direct Brown M.RTM. and Direct Fast
Black D.RTM. (products of Nippon Kayaku Co. Ltd.); acid dyes such
as Kayanol Milling Cyanine 5R.RTM. (product of Nippon Kayaku Co.
Ltd.); basic dyes such as Sumiacryl Blue 6G.RTM. (product of
Sumitomo Chemical Co., Ltd.), and Aizen Malachite Green.RTM.
(product of Hodogaya Chemical Co., Ltd.); or any of the dyes
disclosed in U.S. Pat. Nos. 4,541,830; 4,698,651; 4,695,287;
4,701,439; 4,757,046; 4,743,582; 4,769,360 and 4,753,922, the
disclosures of which are hereby incorporated by reference. The
above dyes may be employed singly or in combination. Combinations
of pigments and/or dyes can also be used. The above dyes are
thermally-diffusible or meltable. The use of a mixture of thermally
mobile materials can also provide additional advantages such as
altering some of the physical properties (e.g., lowering the
melting point).
[0019] In a most preferred embodiment the polymeric matrix is
itself a colorless thermally-mobile material such as a low critical
temperature polymer. Examples of such colorless thermally mobile
polymeric materials have recurring units of the following formula:
1
[0020] wherein:
[0021] R.sup.1 represents cyano, isocyanate, azide, sulfonyl,
nitro, phosphoric, phosphonyl, heteroaryl, or 2
[0022] where
[0023] X is O, S, NR, or N.sup.+(R).sub.2
[0024] R.sup.3 is R, OR, O--M.sup.+, OCOOR, SR, NHCOR,
NHCON(R).sub.2, N(R).sub.2 or N.sup.+ (R).sub.3;
[0025] M.sup.+ is an alkali or ammonium moiety;
[0026] R is hydrogen, halogen, or an alkyl or cycloalkyl group;
and
[0027] R.sup.2 is hydrogen, alkyl or from the same list as R.sup.1;
such that upon image-wise heating the thermally mobile polymeric
material is mixed into the conductive layer.
[0028] Photopatternable conductive layers useful in the present
invention may be prepared from aqueous or solvent based coating
compositions containing an electrically conductive polymer, a
conductivity enhancing compound, and optionally, a film-forming
polymeric binder. These coating compositions can be applied as thin
layers to the substrate or the mixing layer and by drying can be
converted into photopatternable conductive layer elements. For
improved conductivities the dried, photopatternable conductive
layer may be annealed at temperatures of 140.degree. C. or higher
for 10 seconds up to about 10 minutes.
[0029] Preferred electrically conductive polymers for use in the
present invention include polypyrrole/poly (styrene sulfonic acid),
3,4-dialkoxy substituted polypyrrole styrene sulfonate, and
3,4-dialkoxy substituted polythiophene styrene sulfonate.
Especially preferred electrically conductive polymers are
polythiophene of formula (I) 3
[0030] wherein each of R1 and R2 independently represents hydrogen
or a C1-4 alkyl group or together represent an optionally
substituted C1-4 alkylene group or a cycloalkylene group,
preferably an ethylene group, an optionally alkyl-substituted
methylene group, an optionally C1-12 alkyl- or phenyl-substituted
1,2-ethylene group, a 1,3-propylene group or a 1,2-cyclohexylene
group and n is 5-1000.
[0031] Stable colloidal dispersions of suitable electronically
conductive polymer particles can be obtained commercially, for
example, a stabilized dispersion of thiophene-containing polymer
supplied by Bayer Corporation as Baytron P.
[0032] The conductivity enhancing modifier used in the invention
include organic compounds containing dihydroxy or poly-hydroxy
and/or carboxyl groups or amide groups or lactam groups. Suitable
organic compounds containing dihydroxy or polyhydroxy and/or
carboxyl groups or amide groups correspond to
[0033] (a) formula (II)
(OH).sub.n--R--(COX).sub.m (II)
[0034] wherein m and n are independently an integer of from 1 to
20, R is an alkylene group having 2 to 20 carbon atoms, an arylene
group having 6 to 14 carbon atoms in the arylene chain, a pyran
group, or a furan group, and X is --OH or --NYZ, wherein Y and Z
are independently hydrogen or an alkyl group; or
[0035] (b) a sugar, sugar derivative, polyalkylene glycol, or
glycerol compound; or
[0036] (c) selected from the group consisting of
N-methylpyrrolidone, pyrrolidone, caprolactam, N-methyl
caprolactam, or N-octylpyrrolidone.
[0037] Examples of suitable organic compounds containing lactam
groups are n-methylpyrrolidone, pyrrolidone, caprolactam,
n-methylcaprolactam, n-octylpyrrolidone.
[0038] Preferred radicals R are derived from the furan structure or
the pyran structure. Particularly preferred organic compounds) are:
sugar and sugar derivatives such as sucrose, glucose, fructose,
lactose; sugar alcohols such as sorbitol, mannitol; furan
derivatives such as 2-furancarboxylic acid, 3-furancarboxylic acid;
alcohols such as ethylene glycol, glycerol, di- or triethylene
glycol.
[0039] Polymeric film-forming binders useful in photopatternable
conductive layers according to this invention include, but are not
limited to, water-soluble or water-dispersible hydrophilic polymers
such as gelatin, gelatin derivatives, maleic acid anhydride
copolymers, cellulose derivatives (such as carboxymethyl cellulose,
hydroxyethyl cellulose, cellulose acetate butyrate, diacetyl
cellulose, and triacetyl cellulose), synthetic hydrophilic polymers
(such as polyvinyl alcohol, poly-N-vinylpyrrolidone, acrylic acid
copolymers, polyacrylamide, their derivatives and partially
hydrolyzed products, vinyl polymers and copolymers such as
polyvinyl acetate and polyacrylate acid ester), derivatives of the
above noted polymers, and other hydrophilic synthetic resins that
would be readily apparent to one skilled in the imaging arts. Other
suitable binders include aqueous emulsions of addition-type
polymers and interpolymers prepared from ethylenically unsaturated
polymerizable monomers such as acrylates including acrylic acid,
methacrylates including methacrylic acid, acrylamides and
methacrylamides, itaconic acid and its half-esters and diesters,
styrenes including substituted styrenes, acrylonitrile and
methacrylonitrile, vinyl acetates, vinyl ethers, vinyl and
vinylidene halides, and olefins and aqueous dispersions of
polyurethanes or polyesterionomers.
[0040] Solvents useful for preparing dispersions and coatings of
photopatternable conductive layers by the method of this invention
include, but are not limited to water, alcohols (such as methanol,
ethanol, propanol, and isopropanol), ketones (such as acetone,
methyl ethyl ketone, and methyl isobutyl ketone), esters such as
methyl acetate and ethyl acetate, glycol ethers such as methyl
cellusolve, ethyl cellusolve), and mixtures of any of these
solvents. Preferred solvents include water, alcohols, and
acetone.
[0041] In addition to binders and solvents, other components that
are well known in the art may also be included in the
photopatternable conductive layer used in this invention. Such
addenda include but are not limited to matting agents, surfactants
or coating aids, polymer lattices to improve dimensional stability,
thickeners or viscosity modifiers, hardeners or crosslinking
agents, soluble antistatic agents, soluble and/or solid particle
dyes, antifoggants, lubricating agents, and various other
conventional additives readily apparent to one skilled in the
art.
[0042] The photopatternable conductive layers can be applied to a
variety of flexible or rigid supports. The flexible supports are
preferable embodiments of this invention. Typical flexible film
supports are preferred and include but are not limited to,
cellulose nitrate, cellulose acetate, cellulose acetate butyrate,
cellulose acetate propionate, poly(vinyl acetal), poly(carbonate),
poly(styrene), poly(ethylene terephthalate), poly(ethylene
naphthalate), poly(ethylene terephthalate), and poly(ethylene
naphthalate) having included therein a portion of isophthalic acid,
1,4-cyclohexane dicarboxylic acid or 4,4-biphenyl dicarboxylic acid
used in the preparation of the film support; polyesters wherein
other glycols are employed such as, for example,
cyclohexanedimethanol, 1,4-butanediol, diethylene glycol,
polyethylene glycol, ionomers as described in U.S. Pat. No.
5,138,024, incorporated herein by reference (such as polyester
ionomers prepared using a portion of the diacid in the form of
5-sodiosulfo-1,3-isophthalic acid or like ion containing monomers),
polycarbonates, and blends or laminates of the above noted
polymers. Preferred photographic film supports are cellulose
acetate, poly(ethylene terephthalate), and poly(ethylene
naphthalate), and most preferably poly(ethylene naphthalate) that
is prepared from 2,6-naphthalene dicarboxylic acids or derivatives
thereof.
[0043] Suitable supports can be either transparent or opaque
depending upon the application. Transparent film supports can be
either colorless or colored by the addition of a dye or pigment.
Film supports can be surface-treated by various processes including
corona discharge, glow discharge, UV exposure, flame treatment,
e-beam treatment, or treatment with adhesion-promoting agents
including dichloro- and trichloroacetic acid, phenol derivatives
such as resorcinol and p-chloro-m-cresol, solvent washing or
overcoated with adhesion promoting primer or tie layers containing
polymers such as vinylidene chloride-containing copolymers,
butadiene-based copolymers, glycidyl acrylate or
methacrylate-containing copolymers, maleic anhydride-containing
copolymers, condensation polymers such as polyesters, polyamides,
polyurethanes, polycarbonates, and mixtures and blends thereof.
Other suitable opaque or reflective supports are paper,
polymer-coated papers, including polyethylene-, polypropylene-, and
ethylene-butylene copolymer-coated or laminated paper, synthetic
papers, and pigment-containing polyesters. Of these support
materials, films of cellulose triacetate, poly(ethylene
terephthalate), and poly(ethylene naphthalate) prepared from
2,6-naphthalene dicarboxylic acids or derivatives thereof are
preferred.
[0044] The thickness of the support is not particularly critical.
Support thickness of 0.50 to 10 mils (50 .mu.m to 254 .mu.m) are
generally suitable for the materials of the present invention.
[0045] Coating compositions for the preparation of photopatternable
conductive layers can be applied to the aforementioned supports by
any of a variety of well-known coating methods. Hand coating
techniques include using a coating rod or knife or a doctor blade.
Machine coating methods include air doctor coating, reverse roll
coating, gravure coating, curtain coating, bead coating, slide
hopper coating, extrusion coating, spin coating and the like, and
other coating methods well known in the art.
[0046] The photopatternable conductive layer formulations of this
invention can be applied to the support at any suitable coverage
depending on the specific requirements of a particular application.
For example, dry coating weights of the preferred electrically
conductive polymer particles dispersion in a photopatternable
conductive layer are preferably in the range of from about 0.002 to
about 0.5 g/m2. More preferred dry coverage is in the range of from
about 0.003 to about 0.1 g/m2.
[0047] The method of the invention relies on mixing of the
thermally mobile material into the conductive layer. The change in
the resistivity of the conductive layer may result from the mobile
material affecting the inherent conductive properties of the
conductive polymer or as a result of physical dilution of the
conductive polymer in the layer thereby disrupting the original
conductive network. There is usually a certain temperature
threshold below which the mobile materials are unaffected. Thus
under ambient conditions, where the mixing layer may absorb
incident light, no change is induced because the amount of heat
generated from this process is spread out over a long period of
time so that the threshold for the mobile material diffusion is not
reached. To obtain a laser-induced resistivity change according to
the invention, an infrared diode laser is preferably employed since
it offers substantial advantages in terms of its small size, low
cost, stability, reliability, ruggedness, and ease of modulation.
Lasers which can be used in the invention are available
commercially. There can be employed, for example, Laser Model
SDL-2420-H2 from Spectra Diode Labs, or Laser Model SLD 304 V/W
from Sony Corp.
[0048] A thermal printer which uses a laser as described above to
form an image on a thermal print medium is described and claimed in
U.S. Pat. No. 5,168,288, the disclosure of which is hereby
incorporated by reference.
[0049] The following examples are provided to illustrate the
invention.
EXAMPLE 1
[0050] A 0.1 mm polyester support was overcoated with 0.054
g/m.sup.2 of IR absorbing dye (IR Dye-1 below) and 0.38 g/m.sup.2
of polymethycyanoacrylate, molecular weight of about 50,000, from
acetonitrile, with 0.004 g/m.sup.2 of FC 431 surfactant (obtained
from 3M Corporation) to improve coating uniformity. The dried
coating was then overcoated with a layer containing 0.15 g/m.sup.2
of polyethylenedioxythiophene conductive polymer (Baytron P, Bayer
Corp), 0.075 g/m.sup.2 of polyvinyl alcohol as a binder, and 0.004
g/m.sup.2 of an epoxy silane (CoatoSil 1770 is made by OSi
Specialties, a subsidiary of Witco Corp.) applied from an aqueous
formulation containing 5 weight % diethylene glycol added as a
conductivity enhancing compound. The coating was dried for 2
minutes at 100 4
[0051] The film was exposed to a focused laser beam having an
approximate diameter of 25 .mu.m (1/e.sup.2) and 450 mW per channel
at the film plane. Solid areas of 2.54 cm wide were exposed with a
series of drum speeds giving effective exposures as listed in table
1. The resistivity was measured with a two-point probe in each
exposed area and is also listed in table 1.
1TABLE 1 Resistivity versus Exposure Exposure Example 1
(mJ/cm.sup.2) (.OMEGA./square) 2288 >1.0E+12 1144 >1.0E+12
763 >1.0E+12 572 >1.0E+12 458 >1.0E+12 381 >1.0E+12 327
>1.0E+12 286 8.0E+03 0 4.0E+03
[0052] The resistivity of the unexposed film was low (about
4.times.10.sup.3 .OMEGA./square) Above a threshold exposure
(approximately 280 mJ/cm.sup.2 for example 1) a partial increase in
resistivity is observed. At very high exposure (above 1000
mJ/cm.sup.2) the layers of the film are clearly ablated and the
resistivity reaches the limiting value of the support. Examination
of the film, exposed at intermediate exposures (300 to 500 mJ/cm
.sup.2), shows that the resistivity reaches the limiting value
before the conductive layer is ablated. Thus, with optimal exposure
the resistivity of the exposed area can be increased by a factor,
.DELTA., that is at least 8 orders of magnitude higher that the
unexposed areas without removing the conductive layer.
* * * * *